SENSITIVE REVERSED-PHASE LIQUID-CHROMATOGRAPHIC DETERMINATION OF FLUORIDE BASED ON ITS TERNARY-SYSTEMS WITH ZIRCONIUM(IV) OR HAFNIUM(IV) AND 2-(5-BROMO-2-PYRIDYLAZO)-5-DIETHYLAMINOPHENOL

Optimum conditions for the direct reversed-phase LC determination of f luoride based on the ternary M-F--(5-Br-PADAP) complexes [M = Zr-IV or Hf-IV and 5-Br-PADAP = 2-(5-bromo-2-pyridylazo)5-diethylaminophenol] were evaluated. Chromatographic separation was performed with Cls end- capped column with an eluent consisting of acetonitrile- water (85 +15 v/v) mixture of pH 4.0 +/- 0.3 (flow rate 1 mi min(-1)), and the elua te was monitored spectrophotometrically at lambda(max) = 585 nm. The c alibration curves were linear over a wide range of fluoride concentrat ions: from 1 to 110 and 150 ng ml(-1) for the Zr-IV-F--(5-Br-PADAP) an d Hf-IV-F--(5-Br-PADAP) systems, respectively (using a 20 mu l loop). Under such conditions the detection limits mere 0.8 and 0.7 ng ml(-1), respectively, and the quantification limit is 1.0 ng ml-l for both me thods. When a 100 mu l loop was used, the limits of both detection and quantification in the method based on the zirconium system were 0.2 n g ml(-1). Using the proposed method, fluoride was determined directly in tap mater, saliva and an anti-cancer agent for prostatic cancer (Le uprolid).